This invention relates to a photosensitive member containing a specific fluorescent bleaching agent.
In electrophotography, copied images are formed by various kinds of methods. For example, the surface of a photosensitive member is charged and irradiated to form electrostatic latent images thereon, the electrostatic latent images are developed by a developer to be made visible and then the developed electrostatic latent images are fixed directly onto the photosensitive member (referred to as a direct method). In other method, developed electrostatic latent images on a photosensitive member which are made visible by a developer are transferred to a copying paper and then, the transferred images are fixed on the paper (referred to as a powder transferring method). In another method, electrostatic latent images on a photosensitive member are transferred onto a copying paper, the transferred electrostatic latent images are developed by a developer and then fixed on the copying paper (referred to as an electrostatic latent image transferring method).
Known photosensitive materials for forming such a photosensitive member include inorganic photoconductive materials such as selenium, cadmium sulfide or zinc oxide.
These photosensitive materials have many advantages such as low loss of charges in the dark, an electrical charge which can be rapidly dissipated with irradiation of light and the like. However, they have disadvantages. For example, a photosensitive member based on selenium is difficult to produce, has high production costs and is difficult to handle due to inadequate resistivity to heat or mechanical impact. A photosensitive member based on cadmium sulfide or zinc oxide has defects such as its unstable sensitivity in a highly humid environment and loss of stability with time because of the deterioration of dyestuffs, added as a sensitizer, by corona charge and fading with exposure.
Many kinds of organic photoconductive materials such as polyvinylcarbazole and so on have been proposed. These organic photoconductive materials have superior film forming properties, are light in weight, etc., but inferior in sensitivity, durability and environmental stability compared to the aforementioned inorganic photoconductive materials.
Physical properties or electrophotographic properties of a coating layer as a photosensitive member may be adjusted desirably by using an organic photoconductive material of low molecular weight in the combination with a selected binder resin, a selected composition or the like. However, the high compatibility of an organic photoconductive material with a binder resin is required because the photoconductive material is used together with the binder resin.
A photosensitive member prepared by dispersing an organic photoconductive compound of low molecular weight or high molecular weight in a binder resin has problems such as high residual potential caused by many traps of carriers, low sensitivity and the like. Therefore, a charge transporting material is further incorporated in a photosensitive member in order to overcome the problems as above mentioned, and a function-divided photosensitive member of a laminated or a dispersed type has been also proposed, in which charge generating function and charge transporting function are divided by different layers or different dispersed materials.
Many kinds of organic compounds are used as a charge transporting material, which have, however, many problems. For example, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole disclosed in U.S. Pat. No. 3,189,447 is low in compatibility with a binder and liable to separate out. A diarylalkane derivative disclosed in U.S. Pat. No. 3,820,989 is good in compatibility with a binder resin, but changes in sensitivity when used repeatedly. A hydrazone compound disclosed in JP Laid-open No. 54-59143 is relatively good in residual potential properties, but being poor in chargeability and repetition properties.
Repetition properties, light-fatigue properties, or durability properties thereof are required as well as sensitivity and chargeability in order to meet utility of a photosensitive member.
However, an organic photosensitive member has, in general, problems such as unstability in initial surface potential or light decaying properties, remarkable light fatigue and poor durability.
There are proposed, for example, Japanese Patent Laid-open 60-191264 or 59-123845 to improve photosensitivity and durability of a photosensitive member.
Japanese Patent Laid-open 60-191264 discloses that a hydrazone compound is contained in a photosensitive member to achieve excellent photosensitivity and repetition properties of initial surface potential. It is further disclosed that the addition of an acridine dye, a thiazine dye or an oxazine dye is effective to improve photosensitivity. However, the photosensitive member disclosed therein is also unstable in electrophotographic properties such as surface potential, residual potential and the like when used repeatedly.
Japanese Patent Laid-open 59-123845 discloses a photosensitive member having a charge generating layer and a charge transporting layer in which an electron donating compounds such as phenazine, triazole and the like are incorporated into the charge generating layer to improve the injection effectiveness of charges generated in the charge generating layer into the charge transporting layer for improvement of photosensitivity. The objects of this technique, however, are not to improve repetition properties, durability and the like of a photosensitive member, being different from those of the present invention.
On the other hand, Japanese Patent Laid-open 62-249167 discloses that a thioxanthone compound is added into a photosensitive layer to stabilize repetition properties. Japanese Patent Laid-open 62-262053 discloses that a thiuram monosulfide compound is added into a photosensitive layer to stabilize repetition properties. Japanese Patent Laid-open 62-30256 discloses that a triphenylmethane pigment is added to stabilize repetition properties. However, further improvements of repetition properties, durability and the like are required in these photosensitive members.